Lamp to eliminate single frame curtain

ABSTRACT

A projection lamp for use in a motion picture projection system. The lamp comprises a primary incandescible filament one end of which is electrically connected to a lamp lead-in, a first ballast filament one end of which is electrically connected to a lamp lead-in, with the other ends of these filaments being electrically connected. The improvement comprises disposing within the lamp a second ballast filament one end of which is serially electrically connected to the primary incandescible filament and the first ballast filament, and the other end is connected to an individual lead-in. The second ballast filament is thus adapted to be connected as part of the series load with the operating potential applied thereacross to cause the primary filament to incandesce with a low level of intensity to permit an individual film frame to be viewed.

United. States Patent Rainone 1 Feb. 1, 1972 [54] LAMP TO ELIMINATE SINGLE FRAME CURTAIN Primary Examinerwilliam L. Sikes Assistant Examiner V. P. McGraw v [72] lnvemon- "know blame Attorney-A. T. Stratton, W. D. Palmer and Walter Sutclifi [73] Assignee: Westingboue- Electric Corporation, Pittv sburgh, Pa. [57] ABSTRACT [22] Filed: Jan. I5, 1970 A projection lamp for use in a motion picture projection system. The lamp comprises a primary incandescible filament [21] Appl' one end of which is electrically connected to a lamp lead-in, a first ballast filament one end of which is electrically connected [52] US. Cl. .313 13 to a lamp lead-in, with the other ends of these filaments being Jlolk U3 electrically connected. The improvement comprises disposing Field Search I 3 l 5; 1 within the lamp a second ballast filament one end of which is 3 l5/ '2 serially electrically connected to the primary incandescible filament and the first ballast filament, and the other end is [56] Cm connected to an individual lead-in. The second ballast fila- UNITED STATES PATENTS ment is thus adapted to be connected as part of the series load with the operating potential applied thereacross to cause the 3,327,162 6/1967 Wright "313/1 13 primary filament to incandesce with a low level of intensity to 2,924,748 2/ l 960 122 permit an individual film frame to be viewed. 3,310,702 3/l967 Falge ..3 l3/l l3 3,325,667 6/1967 ONeill et al ..3 l 3/] l3 3 Claims, '3 Drawing Figures PATENTEU FEB 1 1972 24 SWITCH POWER 5 UPPLY INVENTOR NICHOLAS J. RAINONE ATTORNEY 1 I mm To Emma-TE SI GLE rams CURTAIN BACKGROUb D or rue INVENTION The incandescent projection lamps used with motion picture film projection systems are high-intensity light sources .which develop a considerable amount of heat. When the projection system operator wishes to stop the film at a particular frame forindividual viewingthe heat of the standard project tion lamp is so intense that if reviewed for more than a few seconds the filth will be damaged or destroyed. It has therefore been the practice to provide a mechanically operated light curtain which can be moved into position between the pioe jection lamp and the film when the film is stopped. This light curtain in effect acts as a heat shield, and also significantly diminishes the light available for projection of the film image when the film is stepped.

This mechanically operated light curtain has proven un-. reliable in operation and expensive to manufacture. It is therefore desired to protect the stopped single frame of the motion picture film ina simple and reliable manner.

It is now common practice to provide motion picture projec'tion lamps with a ballast filament in conjunction with the primary incandescible filament. The ballast filament meets a variety of design considerations including prevention of arcing when t P ry fi amen fa ls. and allowing m re. accurate focusing of primary filament. The ballast filament itself is, not generally used to provide light output,

SUMM RY OF THE INVENTION It has been determined that a unique and convenient way of providing a projection lamp which is conveniently operable for motion picture viewing orfor stop action viewing is had by providing a lamp containing not only a primary incandescible filament and a first ballast filament, but also a second ballast filament. The primary incandescible filament of predetermined impedance is permanently serially electrically connected to the first ballast filament of predetermined impedance with the other ends of these filaments, being con-. nected to a first lead-in and a second. lead-in. A second ballast filament of predetermined impedance has one, end. serially electrically connected tothe first ballast filament and the primary incandescible filament. The other end of the second bal last filament is, connected to a third lead-in. An operating potential is applied across the first and second lead-ins, to provide a high, level of illumination forviewing the moving frames of the motion picture film. The third, lead-in and one of; the first and second lead-ins which is electrically connected to said second ballast; filament through said primary filament and. first ballast filament; are adapted" via conventional switching means to be connected, across the operating potential. .The first or second lead-in being usedresults in the serial electricalconnection of'the, primaryfilament and the firstand second ballast filament, and, the connection of the three filaments as a. serial load impedance across the operating potential. The pri-. mary filamentwillthen incandesce ata lower levelof. illumination for long termviewingofan individual frame of'film.

BRIEF DESERIPTIQ N OF Tl-IE DRAWING FIG. 1 is a schematicshowing an example of the lamp of the invention incorporated into. amotion picture projection, system. 7 l

FIG. 2 is a side; elsyational view of a lamp embodiment of the present invention;

FIG. 3 is. a, front; elevational view of a lamp embodiment of the present invention.

DESCRIPTIONOETHE PREFERRED EMBODIMENT The projection system shown in FIG. 1 comprises the reels l2 fordisposing-midiv feeding the film. 14, a drive system 116 for moving the flelsandithe film, the projection lamp 180i the presentinvention, and the optical system. 20, for projecting the film image .7 They power supply 22provides electrical potential for operatingthe lamp l8 and also the drive system l6. A switching means 24 connects the power supply to the lamp and the drive means. a y I The lamp 18 as shown in FIG. 2 and FIG. 3 comprises a hermetically sealed envelope 26 of light transmissive material. The electrical lead-ins 28a, 28b and 28c are hermetically sealed through the base of the envelope 26, and the portion of the lead-ins within the lamp serve to support the interiorly disposed lamp members. A first lead'in conductor 28a is electr cally connected to one end of the primary incandescible filament 30, which is centrally disposed within said envelope to facilitate focusing the light output. The other end of this primary filament 30 is electrically connected to one end of the first ballast filament 32, the other end of filament 32 is electrically connected to second lead-in conductor 28b. The external portions of lead-ins 28a and 28b are adapted to be connected via switching means 24 to the power input source 22 which is typically 120 volts AC. The second ballast filament 34 is disposed within the envelope, with one end of the second ballast filament 34 directly electrically connected to the end of the first ballast filament 32 at lead-in 28b, and the other end of the second ballast filament 34 is electrically connected to third lead-in conductor 280 which is also connected to switching means 24. Thus, the filaments are adapted so that the. operating potential can be applied across the primary filament 30 and the first ballast filament 32 at lead-ins 28a and 28b, or across all three filaments in series at lead-ins 28a and 280. When the operating electrical potential is applied to the drive system 16 so that the film is advancing at the normal rate, the switching means 24 causes the lamp potential to be applied across lead-ins 28a, 28b so that the primary incandescible filament and the first ballast filament comprise the load. When there is no electrical potential applied to the drive system 16, the switching means 24 causes the lamp potential to be applied across lead-ins 28a, 28c so that all three filaments comprise the load. By way of example, for a typical 150 watt lamp, about 90 watts is expended in the primary filament and about watts in the first ballast filament when an alternating current potential of 120 volts. is applied across lead-ins 28a and 28b. When the second ballast filament is included in the series network by applying the operating potential across lead-ins 28a and 28c, the power expended inthe primary incandescible filament is only about 29 watts, about 20 watts for the first ballast filament, and about 36 watts for the second ballast filament.

The lamp embodiment shown incorporates an integral reflector 36, which is designed to accurately focus the light output of the primary incandescible filament 30 for projecting the film image for viewing. The reflector could, of course, be disposcdoutside the lamp envelope.

The relative impedance for each of the filaments within the lamp are a matter of simple design change depending on the specific operating requirements for the lamp.

Another advantage in using the lamp of the present invention in the improved projector system is the greatly increased light output which can be provided by thus eliminating the light curtain. It has been found possible to double the light output available for still or single frame projection using the lamp. of'the present invention.

I claim:

1'. In a projection lamp for use in a motion picture projection system, which lamp comprises, a sealed light transmissive envelope, a plurality of electrical lead ins sealed through said envelope, a first lead-in is electrically connected to one end of a single primary incandescible filament of predetermined impedance disposed within said envelope to facilitate focusing the light output and which is serially electrically connected to one. end of afirst ballast filament of predetermined impedance disposed within said envelope, the other end of said first ballast filamentbeing electrically connected. to a second lead-in, the improvement comprising disposing a second ballast filamerit of'predeterrnined impedance'within said envelope, one. end of said second ballast filament is serially electrically connected to said primary incandescible filament and said first ballast filament, the other end of said second ballast filament being connected to a third lead-in, said first and second leadin conductors are adapted to be connected across a source of operating potential of predetermined magnitude to cause said primary incandescible filament to incandesce with a predetermined high level of illumination for viewing moving frames of motion picture film, and said third lead-in conductor and the one of said first and second lead-in conductors which is electrically connected to said second ballast filament through said primary filament and first ballast filament adapted to be connected across said source of operating potential, whereby when so connected said primary filament incandesces with a lower level of illumination for long term viewing of an individual frame of said film.

2. The lamp as specified in claim 1, wherein a parabolic reflector is disposed within said envelope and said primary incandescible filament is disposed about the focus of said parabolic reflector.

3. The lamp as specified in claim 1, wherein one end of said second ballat filament is directly electrically connected to said other end of the first ballast filament and the other end of the second ballast filament is directly electrically connected to said third lead-in conductor, and said first and third lead-in conductors are adapted to be connected across said source of operating potential for long term viewing of an individual frame of said film.

I! i l 8 i 

1. In a projection lamp for use in a motion picture projection system, which lamp comprises, a sealed light transmissive envelope, a plurality of electrical lead-ins sealed through said envelope, a first lead-in is electrically connected to one end of a single primary incandescible filament of predetermined impedance disposed within said envelope to facilitate focusing the light output and which is serially electrically connected to one end of a first ballast filament of predetermined impedance disposed within said envelope, the other end of said first ballast filament being electrically connected to a second leadin, the improvement comprising disposing a second ballast filament of predetermined impedance within said envelope, one end of said second ballast filament is serially electrically connected to said primary incandescible filament and said first ballast filament, the other end of said second ballast filament being connected to a third lead-in, said first and second lead-in conductors are adapted to be connected across a source of operating potential of predetermined magnitude to cause said primary incandescible filament to incandesce with a predetermined high level of illumination for viewing moving frames of motion picture film, and said third lead-in conductor and the one of said first and second lead-in conductors which is electrically connected to said second ballast filament through said primary filament and first ballast filament adapted to be connected across said source of operating potential, whereby when so connected said primary filament incandesces with a lower level of illumination for long term viewing of an individual frame of said film.
 2. The lamp as specified in claim 1, wherein a parabolic reflector is disposed within said envelope and said primary incandescible filament is disposed about the focus of said parabolic reflector.
 3. The lamp as specified in claim 1, wherein one end of said second ballast filament is directly electrically connected to said other end of the first ballast filament and the other end of the second ballast filament is directly electrically connected to said third lead-in conductor, and said first and third lead-in conductors are adapted to be connected across said source of operating potential for long term viewing of an individual frame of said film. 